I don’t think that’s evident, either. There’s plenty of ornate architecture that doesn’t commemorate anything.

I doubt that is true at least for the Taj Mahal and even the Arc de Triomphe.

If that's true about the Taj Mahal, it's true about the Spomenik also.

So now what? You origintally made the point to try to distingish between the power of representative art vs abstract art (although I'm struggling to understand what is more representative about the Taj Mahal and the Arc de Triomphe than these also).

to me as Italian it is evident that Arc du Triomphe it's a replica and that's all I can say for sure about it

Otoh it is quite evident to me that Spomenik monuments are there to commemorate something or they would be very different